Re: [PATCH V6 0/3] Rust support for powerpc

[Madhavan Srinivasan <maddy@linux.ibm.com>]

On 2/10/26 2:30 PM, Mukesh Kumar Chaurasiya (IBM) wrote:
> Enable experimental rust support for ppc64le and ppc32be. The patch for
> ppc32 has been provided by Link Mauve[1] and ppc64le support[2] has been
> merged over it. ppc32 needs some toolchain fixes mentioned in the patch
> `rust: Add PowerPC support` and the discussion for that is done here[1].
>
> This has been tested on powernv9 hardware and power10 pseries qemu. I
> I request Link to test the ppc32 part as i don't have a hardware to test
> it out.
>
> [1] https://lore.kernel.org/all/20260204030507.8203-1-linkmauve@linkmauve.fr
> [2] https://lore.kernel.org/all/20260204042417.83903-1-mkchauras@gmail.com

Could see these build issues with the Rust patchset in the compilation 
of powerpc-next-test
This happens when compilation happens only with few threads

# rustc --version
rustc 1.94.0 (4a4ef493e 2026-03-02)

....
   EXPORTS rust/exports_core_generated.h
   BINDGEN rust/bindings/bindings_generated.rs
   BINDGEN rust/bindings/bindings_helpers_generated.rs
   CC      rust/helpers/helpers.o
   EXPORTS rust/exports_helpers_generated.h
   RUSTC L rust/compiler_builtins.o
   RUSTC L rust/ffi.o
   RUSTC PL rust/libproc_macro2.rlib
error[E0464]: multiple candidates for `rmeta` dependency `core` found
  --> rust/proc-macro2/marker.rs:4:5
   |
4 | use core::marker::PhantomData;
   |     ^^^^
   |
   = note: candidate #1: 
/root/.rustup/toolchains/nightly-powerpc64le-unknown-linux-gnu/lib/rustlib/powerpc64le-unknown-linux-gnu/lib/libcore-951759db375eea0c.rmeta
   = note: candidate #2: ./rust/libcore.rmeta

error[E0119]: conflicting implementations of trait `PartialEq` for type 
`fallback::Ident`
    --> rust/proc-macro2/fallback.rs:875:1
     |
869 |   impl PartialEq for Ident {
     |   ------------------------ first implementation here
...
875 | / impl<T> PartialEq<T> for Ident
876 | | where
877 | |     T: ?Sized + AsRef<str>,
     | |___________________________^ conflicting implementation for 
`fallback::Ident`

error[E0277]: `LexError` doesn't implement `std::fmt::Display`
    --> rust/proc-macro2/lib.rs:347:16
     |
347 | impl Error for LexError {}
     |                ^^^^^^^^ unsatisfied trait bound
     |
help: the trait `std::fmt::Display` is not implemented for `LexError`
    --> rust/proc-macro2/lib.rs:204:1
     |
204 | pub struct LexError {
     | ^^^^^^^^^^^^^^^^^^^
note: required by a bound in `std::error::Error`
    --> 
/root/.rustup/toolchains/nightly-powerpc64le-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/error.rs:59:26
     |
  59 | pub trait Error: Debug + Display {
     |                          ^^^^^^^ required by this bound in `Error`

error[E0277]: `LexError` doesn't implement `Debug`
    --> rust/proc-macro2/lib.rs:347:16
     |
347 | impl Error for LexError {}
     |                ^^^^^^^^ unsatisfied trait bound
     |
help: the trait `Debug` is not implemented for `LexError`
    --> rust/proc-macro2/lib.rs:204:1
     |
204 | pub struct LexError {
     | ^^^^^^^^^^^^^^^^^^^
     = note: add `#[derive(Debug)]` to `LexError` or manually `impl 
Debug for LexError`
note: required by a bound in `std::error::Error`
    --> 
/root/.rustup/toolchains/nightly-powerpc64le-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/error.rs:59:18
     |
  59 | pub trait Error: Debug + Display {
     |                  ^^^^^ required by this bound in `Error`

error: aborting due to 4 previous errors

......
But when parallelized with more threads (-j 128) compilation passes with 
out any error
There is some ordering of libcore is messing up I guess (I could be wrong)
(I have removed the warning of unstable features messages here for 
cleaner output)

....
   VDSO64SYM include/generated/vdso64-offsets.h
   RUSTC L rust/core.o
   BINDGEN rust/bindings/bindings_generated.rs
   BINDGEN rust/bindings/bindings_helpers_generated.rs
   CC      rust/helpers/helpers.o
   RUSTC PL rust/libproc_macro2.rlib
   BINDGEN rust/uapi/uapi_generated.rs
   RSCPP     rust/kernel/generated_arch_static_branch_asm.rs
   RSCPP     rust/kernel/generated_arch_warn_asm.rs
   RSCPP     rust/kernel/generated_arch_reachable_asm.rs
clang diag: ./arch/powerpc/include/uapi/asm/ioctl.h:5:9: warning: 
'_IOC_SIZEBITS' macro redefined [-Wmacro-redefined]
clang diag: ./arch/powerpc/include/uapi/asm/ioctl.h:6:9: warning: 
'_IOC_DIRBITS' macro redefined [-Wmacro-redefined]
clang diag: ./arch/powerpc/include/uapi/asm/ioctl.h:8:9: warning: 
'_IOC_NONE' macro redefined [-Wmacro-redefined]
clang diag: ./arch/powerpc/include/uapi/asm/ioctl.h:10:9: warning: 
'_IOC_WRITE' macro redefined [-Wmacro-redefined]
   EXPORTS rust/exports_helpers_generated.h
   RUSTC PL rust/libquote.rlib
   RUSTC PL rust/libsyn.rlib
   RUSTC P rust/libpin_init_internal.so
   RUSTC P rust/libmacros.so
   EXPORTS rust/exports_core_generated.h
   RUSTC L rust/compiler_builtins.o
   RUSTC L rust/ffi.o
   RUSTC L rust/pin_init.o
   RUSTC L rust/build_error.o
   RUSTC L rust/bindings.o
   RUSTC L rust/uapi.o
   EXPORTS rust/exports_bindings_generated.h
   RUSTC L rust/kernel.o
   EXPORTS rust/exports_kernel_generated.h
   LDS     scripts/module.lds
   HOSTCC  usr/gen_init_cpio
   CC      init/main.o
....

Also I see some errors when compiling modules. I am looking at these and 
any help is welcome.
I will pull out Rust patches for now from powerpc-linux next-test branch 
and once this is
restored I will add these patches back to branch for the merge.

Maddy

> Changelog:
> V5 -> V6:
> - Added a missing Tested by from Venkat which got missed since V3
> - Support is marked as Maintained instead of experimental
> V5: https://lore.kernel.org/all/20260210053756.2088302-1-mkchauras@gmail.com
>
> V4 -> V5:
> - Removed a nested ifdef from PPC64 for Little endian toolchain
> V4: https://lore.kernel.org/all/20260209105456.1551677-1-mkchauras@gmail.com
>
> V3 -> V4:
> - Co-developed-by header added in patch 1
> V3: https://lore.kernel.org/all/20260205180429.3280657-1-mkchauras@gmail.com
>
> V2 -> V3:
> - Splited HAVE_RUST in 2 lines
> - BINDGEN_TARGET_powerpc initialized before assigning the same to
>    BINDGEN_TARGET
> V2: https://lore.kernel.org/all/20260204210125.613350-1-mkchauras@gmail.com
>
> V1 -> V2:
> - jump label fix for rust has been moved to a separate patch
> - PPC32 support has been taken
> - rust support has been marked experimental
> - target.json dependency has been removed
> - HAVE_RUST now depends on CPU_LITTLE_ENDIAN for PPC64
>
>
> Link Mauve (1):
>    rust: Add PowerPC support
>
> Mukesh Kumar Chaurasiya (IBM) (2):
>    powerpc/jump_label: adjust inline asm to be consistent
>    powerpc: Enable Rust for ppc64le
>
>   Documentation/rust/arch-support.rst   |  1 +
>   arch/powerpc/Kconfig                  |  2 ++
>   arch/powerpc/Makefile                 |  7 +++++++
>   arch/powerpc/include/asm/jump_label.h | 23 +++++++++++++----------
>   rust/Makefile                         | 10 +++++++++-
>   5 files changed, 32 insertions(+), 11 deletions(-)
>